The present invention relates to a liquid boundary detecting method and apparatus and a liquid removing method and apparatus which are used in removing a first liquid layer from a liquid, such as blood, that is separated into at least the first liquid and a second liquid layer.
It is sometimes necessary to separate an object liquid such as a body liquid, for instance, blood into a first liquid layer and a second liquid layer, and to remove the first liquid layer (supernatant liquid), i.e., serum from the second liquid layer.
To do this, a blood object is placed in a container and, for instance, centrifuged into a first liquid layer and a second liquid layer (two-layer state) that exist in the container. The first liquid layer is an upper liquid layer and the second liquid layer is a lower liquid layer.
Conventionally, to remove the upper liquid layer from the lower liquid layer by sucking up the former, an operator sucks up the upper liquid layer with a syringe or the like while watching the region of the upper liquid layer.
Alternatively, the boundary between the upper liquid layer and the lower liquid layer is detected using ultrasonic waves or light, or by way of current conduction, and an operator removes the upper liquid layer by sucking it up with a syringe etc. to the detected boundary.
However, the former, manual removing operation has the following problems. The operation of extracting an upper liquid layer (supernatant liquid) such as a human body liquid is indispensable in medical examinations, for instance, and the manual removing operation cannot accommodate the amount of tests that has greatly increased in recent years.
Further, in sucking up the upper liquid layer with a tube (also called a tip), the tip portion of the tube may touch and be contaminated by the lower liquid when it comes close to the boundary between the upper and lower liquid layers.
On the other hand, in the method of detecting the liquid boundary, the upper liquid or lower liquid may be changed in quality by application of ultrasonic waves, light, or current.